Aluminium Graphite Composites

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Winfred Reeves
7 years ago
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1 a schunk company Aluminium Graphite Composites

2 Aluminium Graphites are Metal Matrix Composites (MMC) for high reliability applications in power electronics. Aluminium Graphite is manufactured by Hoffmann Elektrokohle, located in Bad Goisern, Austria. The company has well over six decades worth of experience in the field of graphite-materials development and production, giving it a worldwide presence in industries utilizing carbon-based products. Parts made of Aluminium Graphite effectively remove heat from hotspots and reduce mechanical tension within the assemblies. This leads to an improvement in the overall reliability of the electronic system.

3 Thermal Conductivity in W/m.K Si N 3 4 Si SiC W AlN Mo Kovar CuW GaN BeO ALG2208 ALG1808 GaAs CuMoCu Al O 2 3 CuMo AlSiC AlSi Ni Au Fe Cu Ag Al Coefficient of Thermal Expansion in 10-6/K Thermal Management with Aluminium Graphite Increased power densities, high reliability in extreme operating environments, as well as high levels of integrations are challenges faced by current power electronic systems. These are made up of a variety of materials, such as metals, semiconductors, and insulators, with a range of different characteristics. In order to work optimally, the thermal conductivity and the coefficient of thermal expansion (CTE) must be well-atuned within the various materials as they are determining factors in the reliability and performance of the current assemblies. Aluminium Graphite (ALG) possesses a desireable combination of aforementioned thermal properties to make it an ideal solution to thermal management problems in power electronics. Aluminium Graphite - Production & Properties Based on our wide-ranging knowledge of graphite materials, Hoffmann Elektrokohle has developed different Aluminium Graphite materials, namely ALG1808 and ALG2208. Both ALG materials are produced by pressure infiltration of porous graphite by liquid aluminium. The merger of these two materials creates a new composite that incorporates the advantageous properties of both. ALG materials stand out due to their combination of high thermal conductivity, adaptable coefficient of thermal expansion, and very low density (lower than both copper and aluminium). These properties, in particular the CTE, produce ALG parts for power electronics applications that lead to a low stress assembly, high thermal and power cycling capabilities, improved reliability, and consequently an extended lifetime for the device. Properties ALG1808 isotropic ALG2208 anisotropic Orientation x/y/z x/y z Thermal Conductivity (25 C) in W/m.K Coefficient of Thermal Expansion (25 C) in 10-6/K Density in g/cm³

4 Customer-Specific Designs The versatile machineability of Aluminium Graphite means that diverse shapes (from simple surfaces to complex geometries) can be attained. These can be further metallized to provide a solderable surface. Machining Blocks of Aluminium Graphite are processed using common machining techniques, such as cutting or milling, to produce user-defined parts. Complex features such as holes, pedestals or pin fins are easily produced. The surface quality depends on the finishing method, the processing parameters, and the application requirements. Plating options Aluminium Graphite parts can be plated to provide suitable surfaces for the further processing by customers. Therefore, coating technologies, such as electro plating or electro-less plating can be used to apply nickel or other metallizations. Once the ALG has been plated, the CTEs of Aluminium Graphite and the substrate or device can interact optimally.

5 Applications With its wide range of properties and combinations thereof, Aluminium Graphite finds applications in many different areas of thermal management. Parts may be used as active or passive cooling solutions in power electronics. Base Plates and Coolers The CTE of ALG base plates or coolers makes them compatible with commonly used ceramic substrates, such as DBCs (Direct Bonded Copper), for high reliability power applications. The parts stand out due to their high thermal conductivity and low density, which is particularly important for weight sensitive applications in traction and transportation. Heat Sinks and Heat Spreaders The thermal properties and the possibility of making miscellaneous parts with different geometrical shapes makes ALG a suitable heat sink material with the additional advantages of a low CTE and a low density. ALG2208 parts are predestined for heat spreading applications as their high lateral thermal conductivity efficiently removes heat from hotspots. Discs and Rings Thin round discs and rings made of ALG can be used as contact materials in press-pack diodes or thyristor modules. The parts act as strain buffers between the copper heat sinks and the silicon device to improve the overall reliability of the system. They are a viable alternative to conventional molybdenum discs and rings.

6 Hoffmann & Co Elektrokohle AG Au Bad Goisern am Hallstättersee Austria Phone Fax /2014

Thermal Management Solutions for Printed Circuit Boards used in Digital and RF Power Electronics and LED assemblies

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